Since the late 1800s global temperatures have risen by an average of
0.5°C - 0.7°C and forecasts suggest that trend will accelerate.
Increases of 0.2°C are expected every 10 years over the next century
and that could have severe implications for tree fruit growers.

Orchards, particularly intensive production, require an adequate
water supply during the growing season but it becomes more critical
for yield and quality in the spring and summer. It is during this
stage of the production cycle that the fruit moves from growth driven
by cell division to increasing size through fruit cell expansion. This
fruit fill is heavily dependent on water supply and it coincides with
a seasonal period when water is most likely to be scarce.

As well as the reduced rainfall during the summer, drier, hotter
weather increases the heat load on the tree. This adds to the rate of
evaporative loss from the leaves and more water is drawn up from the
soil as the process of transpiration accelerates. Evaporative losses
also occur from the soil surface removing more moisture from the area
around the roots, where it is needed most.

Orchards require an adequate water supply during the growing season but it becomes more critical for yield and quality in the spring and summer

So, as global temperatures rise this process is likely to increase -
putting more pressure on the grower to provide additional water
through irrigation to maintain crop yield and quality (fruit size).
With a growing world population that pressure on water use and food
production will intensify.

Some climatologists predict that by the 2050’s agricultural water
demand in drier areas of the UK will have risen by 180% of current
demand. Already in parts of the USA and Australia, rivers are so
heavily exploited by agricultural abstraction they no longer reach the
sea. For example, 90% of the water in the lower reaches of the
Colorado River is abstracted to serve agriculture.

Environmental concern is rising and as competition for water has
grown, so legislation governing its use has become tougher and more
expensive to comply with. It means growers face greater competition
for a potentially more expensive, yet dwindling, supply of water in
the future.

Tree fruit growers will not only have to provide crops with
additional water, they will have to adopt a range of measures to
conserve it and minimize waste across all the growing inputs.

Looking to the soil itself there has been a marked reduction in
organic matter levels across the world where modern agricultural
methods have been employed. So, applying organic matter to
re-condition and restructure soil will help cut losses by enabling it
to better retain moisture and nutrients. Another option to reduce
water loss is the laying of organic mulches or polythene around the
tree base. This cuts the level of moisture loss through soil surface
evaporation, especially in the area around the root where it is needed most.

Directing water to the root itself will also be an increasingly
important aim of irrigation systems. Overhead irrigation equipment,
which is still widely used, has been found to lose at least 18% of the
water output through evaporation. This type of equipment could be
outmoded as rising water costs and environmental concern put the
grower under pressure to look for alternatives. Instead investment is
more likely in water systems which pipe moisture beneath the soil
surface to the root zone to ensure losses are minimized.

Other management techniques, which match the tree’s water demand more
closely with the amount supplied, may also become more prevalent.
While this is notoriously difficult on a field-scale system which is
exposed to changeable weather, it is possible to adapt techniques seen
in soft fruit trials. These have tailored moisture supply to plant
demand and have seen savings of 40-70% in water use.

Variety choice could play an important role too. Genetic traits mean
different varieties perform better than others in drier conditions. It
may also be that harvest could be brought forward, so lessening the
number of summer days when irrigation is required. Traditionally,
harvest takes place in the autumn, but higher temperatures mean the
crop may mature earlier. Moving away from a calendar-based harvest
date and focusing more on the apple’s maturity could mean a more
flexible approach is taken and summer harvesting could be achievable.

Widely used overhead irrigation equipment has been found to lose at least 18% of the water output through evaporation

As water prices rise investment in large-scale conservation such as
on-farm reservoirs or storage tanks, filled by winter rain, could
become an economical proposition. While extended dry periods in spring
and summer months are more common, winters in many parts of Europe
have become milder and wetter.

Climatologists predict that flooding incidences will be more frequent
in the future and this represents a further challenge for the grower
in the future. Too much water is as bad as too little, especially when
trees are dormant in the early spring and winter. Saturated soils
block oxygen need for the roots to metabolize and function. Reducing
the threat of flooding is more down to site choice and geographical location.

The growers of the future may look to site orchards on slopes that
are freer draining in the winter. Mild, wet winters also provide
favourable conditions for pests and diseases to overwinter on leaf
matter or soil and present a greater risk in the following growing season.

Therefore, the overall impact of climate change may well be to see
apple and pear growing regions shift from their current sites to
cooler climes to reduce the risks of pest and disease build up and
summer drought.

Click
here to read part 1 of our focus on the effects of
climate change to fruit growers

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